The endowments at 23 private colleges and universities in Eastern Massachusetts increased an average of 17.65 percent between the 2012 and 2013 fiscal years, according to a BBJ review of annual tax filings from the institutions.

The increases ranged from, on the low side, 3.3 percent in the case of Olin College of Engineering to, on the high side, 123.78 percent in the case of Regis College. The percentage increases in the endowments reflect investment returns and gifts as well as the amounts schools spent out of the endowments on scholarships, grants, facilities and programs.

At $31.6 billion, Harvard University’s endowment was, not unexpectedly, the largest in the group for the 2013 fiscal year. The figure reflects a 6 percent increase over the previous year. Harvard’s investments generated a 10 percent return in 2013.

The second largest endowment belonged to the Massachusetts Institute of Technology, which reported $11 billion in the 2013 fiscal year, a 7 percent increase over 2012. MIT’s investment return was 10.4 percent in 2013.

Some school endowments benefited from accounting changes. For example, the soaring year-over-year endowment increase that Regis College reported was not related to an investment strategy, but rather was related to the school’s inclusion in the endowment $17 million worth of property on its east campus, said Thomas Pistorino, chief financial officer of Regis College.

Regis reclassified the property and included the value in its endowment when the college decided to not pursue a senior housing project on the eastern part of its campus, he said.

More recently, the board of trustees for Regis College voted in May to change its fund managers and investment strategy, weighting it more heavily toward equity investments, Pistorino said.

Ten years ago, when Regis experienced a serious financial deficit,the school's investment portfolio was split between 60 percent fixed income investments and 40 percent equity investments. Now Regis is flip-flopping that investment mix to include 60 percent equity investments and 40 percent fixed income investments, he said.

“There’s an overall sense that we don’t need the security of fixed income and we’d be better suited to have the greater returns from the investment portfolio,” he said

A similar shift has taken place gradually at Curry College, said Richard Sullivan, chief financial officer. Curry College had a $76 million endowment in fiscal year 2013 and saw its endowment increase 23.5 percent year over year.

Its portfolio returned 20.1 percent — which, aside from Regis, was the largest investment return in the group of 23 schools included in the BBJ analysis.

Curry College has gradually changed its investment mix over the past five years, Sullivan said. For instance, the school's asset allocation on May 31, 2009, was 80 percent fixed income investments and 20 percent equities, he said. By May 31, 2013, the split was 39 percent fixed income investments and 61 percent equities, Sullivan said.

“I’d say that our allocation reflects where we think the opportunities are,” said Sullivan.

At The Boston Conservatory, the changes in investment approach are even more pronounced. The school reported a $7.9 million endowment in fiscal year 2013, the smallest in the group of 23 schools the BBJ reviewed. Its portfolio returned 8.25 percent that year.

In April 2013, the conservatory changed its investment adviser, moving from Boston Private Bank & Trust Co. to First Republic Bank. Like Regis and Curry, the music college also shifted its asset mix to favor a heavier mix of equities over debt securities.